During pregnancy, both vasculogenesis and extensive angiogenesis are required for successful fetal and placental development. Vasculogenesis is a process in which endothelial cells differentiate and proliferate within a previously avascular tissue, while angiogenesis refers to the remodeling process that occurs after the initial vascular network is developed. A successful pregnancy requires an appropriate balance between angiogenic and anti-angiogenic processes, and several angiogenic and anti-angiogenic factors are important for successful reproductive function.
An imbalance in angiogenic and anti-angiogenic factors has been observed in several obstetrical complications including miscarriage, implantation failure, early preeclampsia (PE), a subset of late PE, small for gestational age (SGA) neonates, preterm labor, fetal death (FD), placenta-related causes of FD, fetal growth restriction, placental abruption, mirror syndrome (i.e. Ballantyne's syndrome), molar pregnancy, twin-to-twin transfusion syndrome, and placental findings suggestive of maternal floor infarction.
Several large epidemiological studies have found placental lesions in the majority of pregnancies resulting in FD, particularly lesions that are consistent with maternal vascular underperfusion. FD has also been associated with abnormal uterine artery Doppler velocimetry (UtADV) findings and abnormal concentrations of biochemical markers associated with placental function, each measured during the first two trimesters. There is currently no effective way to identify women at increased risk of FD.